Chen Y, Sokoloski J A, Chu E, Sartorelli A C
Department of Pharmacology, Cancer Center, Yale University School of Medicine and VA Connecticut Healthcare System, New Haven 06520, USA.
Leuk Res. 1998 Aug;22(8):697-703. doi: 10.1016/s0145-2126(98)00054-x.
The expression of a number of housekeeping enzymes of DNA biosynthesis was measured in HL-60 promyelocytic leukemia cells undergoing monocytic/macrophagic differentiation following treatment with 12-O-tetradecanoylphorbol 13-acetate (TPA) or 1alpha,25-dihydroxyvitamin D3 (vitamin D3). Progressive decreases in the steady-state levels of the mRNAs for thymidylate synthase, topoisomerase II, and hypoxanthine guanine phosphoribosyltransferase occurred following exposure to TPA or vitamin D3. In contrast, the steady-state levels of the mRNAs for thymidine kinase, topoisomerase I, and DNA polymerase-alpha did not decrease until days 3-5 of treatment with vitamin D3 and then progressively declined thereafter. The mRNAs for thymidine kinase and topoisomerase I decreased slightly and the mRNA for DNA polymerase-alpha by 30-40%, and then remained constant between days 1 to 3 of treatment with the phorbol ester. The M2 subunit of ribonucleotide reductase exhibited an even greater difference, with no change in the steady-state concentration of mRNA over 3 days of exposure to TPA or vitamin D3. On days 5-7 of treatment with vitamin D3, essentially complete loss of the expression of the mRNA for the M2 subunit of ribonucleotide reductase occurred. Measurement of the enzymatic activities of thymidylate synthase and thymidine kinase in cells exposed to either of the inducers of maturation corroborated the findings at the level of the mRNAs, with corresponding decreases in the activity of these enzymes. The results indicate that the down-regulation of the expression of housekeeping enzymes of DNA replication occurs as late events in HL-60 cells undergoing monocytic/macrophagic differentiation, implying that the decreases in their gene expression are the result of the termination of proliferation rather than an initiating event in the cessation of DNA biosynthesis.
在用12 - O - 十四烷酰佛波醇 - 13 - 乙酸酯（TPA）或1α,25 - 二羟基维生素D3（维生素D3）处理后经历单核细胞/巨噬细胞分化的HL - 60早幼粒细胞白血病细胞中，对一些DNA生物合成持家酶的表达进行了检测。在用TPA或维生素D3处理后，胸苷酸合成酶、拓扑异构酶II和次黄嘌呤鸟嘌呤磷酸核糖转移酶的mRNA稳态水平逐渐下降。相比之下，胸苷激酶、拓扑异构酶I和DNA聚合酶α的mRNA稳态水平直到用维生素D3处理第3 - 5天才开始下降，此后逐渐下降。在用佛波酯处理的第1至3天，胸苷激酶和拓扑异构酶I的mRNA略有下降，DNA聚合酶α的mRNA下降30 - 40%，然后保持不变。核糖核苷酸还原酶的M2亚基表现出更大的差异，在暴露于TPA或维生素D3的3天内，mRNA的稳态浓度没有变化。在用维生素D3处理的第5 - 7天，核糖核苷酸还原酶M2亚基的mRNA表达基本完全丧失。对暴露于任何一种成熟诱导剂的细胞中胸苷酸合成酶和胸苷激酶的酶活性进行测定，在mRNA水平上证实了这些发现，这些酶的活性相应降低。结果表明，DNA复制持家酶表达的下调是HL - 60细胞单核细胞/巨噬细胞分化后期的事件，这意味着它们基因表达的降低是增殖终止的结果，而不是DNA生物合成停止的起始事件。
